Content is often displayed in a computing system within a window or viewer. When that viewer is smaller that the content, one or more scrollbars may appear along the sides of the viewer. For instance, if the content is taller than the viewer, a vertical scrollbar will appear at the right or left side of the viewer allowing the user to scroll up and down through the content. Alternatively or in addition, if the content is wider than the viewer, a horizontal scrollbar will appear at the upper or lower side of the viewer, allowing the user to scroll right or left through the content.
A scroll bar typically includes four essential components; two arrow controls, a track, and a thumb. For vertical scrollbars, there is an up-arrow at the top of the scrollbar and a down-arrow at the bottom of the scrollbar. For horizontal scrollbars, there is a left-arrow at the left of the scrollbar and a right-arrow at the right of the scrollbar. The track extends between the two arrow controls. The length of the track represents the entire extent of the content in the scrollable direction served by the scrollbar. The thumb is a rectangular control that may be slid along the track in order to move through the content in the scrollable direction served by the scrollbar the length of the thumb in the direction of the track in proportion to the entire length of the track represents that proportion of the content that is currently displayed. The position of the thumb within the track represents the relative position of the currently viewed portion of the content with respect to the entire extent of the content in the scrollable direction served by the scrollbar.
Such scrollbars are typically always present in the viewer and occupy viewer space so long as the content being displayed is larger than the viewer. Furthermore, if there are several layers of nested viewers, there may be likewise be nested scrollbars since each viewer may have one or more scrollbars. In order to scroll within the appropriate viewer, the user should find the appropriate scrollbar amongst multiple nested scroll bars.
In order to use a scrollbar, a user moves the cursor from wherever it is, to the appropriate navigation controls within the appropriate scroll bar. If the user is to change the type of scrolling to be performed, further cursor movement might be needed. For instance, if one is using the down-arrow to scroll downward, and the user is now to scroll upwards, the user moves the cursor up from the down-arrow control to select the up-arrow control, or clicks on the scroll bar above where the thumb is displayed. The scroll wheel is one advancement that provides further efficiency by not requiring that the mouse be within the confines of the scrollbar in order to operate the scrollbar. However, the scroll wheel is often used for multiple purposes such as scrolling and zooming, making it sometimes ambiguous to the user as to what the scroll wheel will do in a given context.